Right now the difference is that Google Public DNS does not use any sort of redirection or display any ads. If a host (domain name, web address, etc…) doesn’t resolve, it will just fail. With OpenDNS, they hijack these failures and redirect you to a search page that displays ads and makes them money.

From the administrator or customer point view there are things like stats, control panels, and more – all in OpenDNS. Google Public DNS seems to be focused differently. At least for now.